In order to conveniently store and handle large-format sheets of paper, film materials, or the like, such as engineering shop drawings or architectural construction plans or the like, it is generally desired to fold these large sheet goods into a smaller format, preferably a standardized format such as DIN size A4 (297.times.210 mm) for example. The folded sheets are then provided with binding holes near an edge thereof, so that the folded sheets can be bound in a ring binder. In this context, the sheets must be folded in such a manner that the legend block, or parts list, or other descriptive information typically provided on such drawings appears on the top face or section of the folded sheet when it is arranged in the binder, so that the folded drawing sheet can be conveniently recognized and identified.
Machines and methods for folding such large-format drawings or the like in a zig-zag fashion, and for properly orienting the drawing sheets so that the descriptive legend information appears on the top folded face are already known, for example as disclosed in U.S. Pat. No. 5,045,039 (Bay) and U.S. Pat. No. 5,320,340 (Bay) of the present inventor. The entire disclosures of U.S. Pat. No. 5,045,039 and U.S. Pat. No. 5,320,340 are incorporated herein by reference.
However, it has been difficult in the prior art to provide holes in a binding margin of the folded sheets in such a manner that the sheets can be unfolded while they remain bound in a ring binder. For example, a conventional method involves gluing or otherwise adhering a protruding binding margin onto an edge of the folded sheet, whereby the binding holes could be provided in this added, protruding binding margin. However, such a procedure is inconvenient and involves manual operations that are time-consuming, costly, and prone to inconsistency and misalignments, for adhering the protruding binding margin onto the sheet.
German Patent Publication 2,618,257 discloses a method by which large-format sheet materials are first folded lengthwise in a zig-zag fashion in such a manner that a protruding binding margin remains along the left edge of the lengthwise folded sheet. In other words, the sheet is not uniformly folded edge-to-edge, but rather is folded with an offset so that one edge of the folded sheet protrudes from the other folded plies or sections of the sheet. Next, the sheet is folded one or more times in a crosswise direction, and binding holes are provided only in the lowest fold ply or section of the protruding binding margin. If binding holes are provided in all of the folded layers or sections of the binding margin, then the sheet could not be folded while it remains bound in the ring binder.
However, the plies of the binding margin not having holes therein would tend to interfere with the rings of the binder. Thus, as a next step, notches or cut-outs that are open at the edge of the sheet must be provided along the binding margin in the folded layers above the bottom layer in alignment or registration with the binding holes provided in the bottom layer. These open-edge notches are necessary so that the upper folded layers of the folded sheet do not interfere with the binder rings, and so that the folded sheet can be unfolded without being removed from the binder, while the lowest folded layer remains bound with the binding holes engaged on the binder rings.
The above mentioned open-edge notches have typically in the past been formed in large sheet materials, such as blueprints, or photostat prints, or electrostatic copy prints for example, by manually laying out the sheets in a flat, non-folded condition on a large separate cutting table. On this table, the open-edge notches are cut out, for example by using a rotating circular knife. Thereafter, the sheet was then folded either by hand or by being fed into a folding machine. Such manual operations are relatively slow, labor intensive, and prone to errors, and cause an interruption in the continuous automated production of numerous folded large-format sheets, i.e. the manual operation forms a bottle-neck between a plotter or copying machine which outputs the sheets, and the folding machine. In systems in which large-format drawings or the like are continuously output by a plotter or other image producing apparatus, and then the flat sheets are fed directly to an adjacent or connected folding machine, it is no longer possible to carry out a manual operation for providing the open-edge notches in the typical manner.